mod_muc_http_auth: Allow for enabling/disabling per user host IMPORTANT: This is a breaking change. The `muc_http_auth_enabled_for` and `muc_http_auth_disabled_for` options are now maps (with user hosts as keys) and not sets.

This module lets you block connections to any remote servers not on a
whitelist.

``` {.lua}
s2s_whitelist = {
    "example.org",
}
```